1. Field of the Invention
This invention relates to a connection construction of a turning angle detector for detecting a turning angle and, more particularly, to a connection construction of connecting mutually the shaft of a body to be detected with the shaft of a potentiometer, rotary switch, code plate, etc. accommodated in the turning angle detector, which will be incorporated in mounting, for example, a throttle opening-degree detector for detecting the degree of opening of a throttle valve.
2. Description of the Prior Art
An example of conventional turning angle detectors of the above kind is disclosed in Japanese Utility Model Laid-Open No. 57-99109 which concerns the technique of throttle opening-degree detector.
The aforementioned technique will be described with reference to the sectional view of FIG. 6 showing one conventional throttle opening-degree detector.
The conventional throttle opening-degree detector comprises a holder 33 having a brush 32 which turns along a pre-determined locus inside a case 31 with interlocked relation to a throttle valve shaft 34, a potentiometer composed of a resistor body 35 disposed so as to contact slidingly with the brush 32 on the turning locus of the brush 32 which generates an electrical continuous signal in response to the turning angle of the throttle valve shaft 34, a sleeve 37 secured to the case 31 concentrically with the rotary shaft of the brush 32, and a joint 36 which is coupled with the holder 33 so as to restrict the movement in the circumferential direction of the holder 33 while making free the movement in the radial direction thereof, fits loosely in the sleeve 37 so as to leave a gap 39 therebetween spreading in the radial direction, and transmits the rotation of the throttle valve shaft 34 to the brush 32 forming the potentiometer.
To integralize the holder 33 and sleeve 37 the holder 33 has a metallic bearing portion 33a. The connection between the holder 33 and joint 36 is designed so that an arm 36a of the joint 36 is pinched by a strut portion 33b of the holder 33 so as to prevent the difference in movement of the circumferential direction from appearing therebetween.
Accordingly, as the throttle valve shaft 34 turns, the joint 36 turns and the arm 36a moves the strut portion 33b pinching that arm in the circumferential direction. As a result, the holder 33 turns and the brush 32 forming the potentiometer is slid. Thus, by means of the output of the potentiometer the turning angle of the throttle valve shaft 34 can be detected.
The throttle opening-degree detector of the foregoing kind has the gap 39 between the sleeve 37 secured to the case 31 and the joint 36 secured to the point of the throttle valve shaft 34, and this gap 39 absorbs a mounting error arising at the time of mounting the throttle opening-degree detector to a throttle body, strain of the throttle valve shaft 34, and the like.
However, the respiration action of the gap 39 is promoted owing to a change in temperature of the throttle body and like parts, whereby water tends to infiltrate into the throttle opening-degree detector. If water infiltrated adheres to the brush 32 or resistor body 35 forming the potentiometer, the output value of the potentiometer is influenced, metallic parts and the like inside the throttle opening-degree detector are corroded, and the lifetime of the throttle opening-degree detector is shortened.